Light control means



June 12, 1956 c. w. MCCORMICK LIGHT CONTROL MEANS Filed May 12. 1949 2 Sheets-Sheet 1 SUN AT L sun AT V O NOON l {I SUN AT IN V E N TO R 672a rles M M: CormzcK M ATTORNFV LIGHT CONTROL MEANS 2 Sheets-Sheet Filed May 12, 1949 3 4 DP W 8 6 w K \m M m a 4 5% m M M w 8 INVENTOR Charles M4 M6 Cormjm.

ATTORNEY v United States Patent LIGHT CONTROL MEANS Charles W. McCormick, Meriden, Conn.

Application May 12, 1949, Serial No. 92,933

9 Claims. (Cl. 2062) This invention relates to light control means by which the light entering a room, and the angle or time at which it enters such room, may be controlled. More particularly it relates to means for controlling the natural daylight entering a room, and especially to means for controlling the period during a day in which sunlight is permitted to pass directly through a window or windows into such room.

Gne of the chief problems encountered in the design of school buildings, ofiices, studios, factories and similar buildings, in which occupants normally maintain a relatively fixed position during their working hours, has been that of providing proper illumination, both natural and artificial, in order to prevent eyestrain and to promote maximum working efiiciency. Natural daylighting of such rooms is generally preferred and is normally utilized a One of the principal to the maximum extent possible. disadvantages in the use of natural light, however, is the fact that over certain periods of the day, depending on the geographical location of the building and the particular window exposure, rays of the sun pass through the window and fall directly onto desks, tables or other working surfaces in the room, thereby producing a highly undesirable glare which is extremely fatiguing to anyone required to work under such conditions. Furthermore, the sunlight may enter the room at such an angle as to strike the occupants face-on, thus blinding them and making work impossible.

Numerous means have been adopted to overcome this difliculty, some of the more common devices being roll shades, curtains or Venetian blinds on the inside of the windows, or awnings of various types on the outside of the windows, for example. Generally these devices, however, not only exclude the undesired direct rays of the sun, but also much, if not all, of the indirect sky light which is desired to give sufiicient illumination. This is particularly true of the roll shade and conventional awning, for example, where in both instances a direct barrier is interposed not only to the suns direct rays but to all other external light as well, requiring the illumination in the room to be supplemented by artificial light in many cases.

Some attempts have been made in the prior art to provide light control means which are effective to intercept the direct rays of the sun without, at the same time, shutting out too much of the natural indirect light. At best,

a compromise has been achieved, as in the conventional horizontal slat or louvered Venetian blind, for example, in which a considerable portion of indirect light is sacrificed in order to get satisfactory sunlight control. Moreover, devices of this type are attended by the further disadvantage that they must be periodically adjusted during the day to give the desired light control, and unless the adjustment is made at regular intervals during the day by someone having a knowledge of proper illumination requirements, the result is quite apt to provide no real improvement at all.

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In addition to the foregoing disadvantages, external awnings of the slatted type, which have sometimes been employed, are necessarily subjected to severe weathering and must be constructed accordingly. This necessarily makes such devices relatively expensive and often rather cumbersome. Moreover, their installation is also expensive, especially so where it is desired to enable them to be controlled or adjusted from within the building.

It is a purpose of the present invention, therefore, to provide a simple but eifective means for controlling the natural light which is permitted to enter a room. More especially, it is a purpose of the invention to provide means which will exclude the direct rays of the sun for any desired period or periods of the day, without, at the same time, shutting out the indirect or sky lighting (i. e. diffused light) necessary for eifective illumination of a room.

In general, the light control device of the present invention comprises a plurality of thin, slat-like louvers arranged in spaced parallel alignment across the face of a window or windows, the louvers being disposed vertically and extending downward from the top of such window or windows. By this arrangement, the face of the window is, in eifect, divided into a series of parallel, vertical light-transmitting passages. For any particular building of given latitude above or below the equator and for any particular window exposure (i. e., north, south, east or west), the spacing of the louvers, their width and angular position with respect to the plane of the window are so correlated by the teaching of the present disclosure that the direct rays of the sun during the latters travel from horizon to zenith and back are intercepted by the slat-like louvers during a predetermined period of the day. Thus, by way of example, a window facing a southerly direction may be provided with a blind or shutter constructed in accordance with the present invention whereby the direct rays of the sun can be prevented from passing into the room during a morning period, a morning and an afternoon period, or an afternoon period alone, without any adjustment, or at most a single pre-set adjustment, of the blind being necessary during the day. That is to say, a single period or several periods of excluding the direct sunlight at selected times of the day may be provided. Also, once the proper correlation of the above factors of louver spacing, width and angular setting has been determined, not only may adjustment of the blind during any one particular day be unnecessary, but in some instances, depending on the latitude of the particular location, a design may be arrived at which makes adjustment of the blind unnecessary throughout an entire year even with changes in declination of the sun which occur during that time.

In the use of blinds of the present invention, unlike those of the types now commonly used, the view horizontally out of a window is not completely shut off from all positions in a room. This allows occupants positioned in a room, such as a schoolroom, for example, to

have normal view out of at least one window in the room from their respective positions, and natural dayli ht is, of course, permitted to enter in the same direction. Following out the example of the schoolroom farther, it will be apparent from What has already been said that by proper design, the blind may be constructed to intercept the passage of direct light from all angles within the horizontal arc through which the sun travels during a particular period of the day, while still leaving unimpeded the entrance of light from angles outside this given are. It is possible, also, to employ the blind for controlling sky glare alone, as on the north side of a building located in the northern hemisphere, where entrance of direct rays of the sun is not encountered. In

such use, the design of the blind is affected only by the requirement of preventing sky glare within an are on either side of the normal forward line of sight of the person seated in the room, which is considered consistent with good lighting practice. Commonly, direct light entering within an arc of about 50 on either side of such forward line of sight has been deemed undesirable for good lighting conditions.

A still further feature of the invention is the provision of simple frame means for supporting a plurality of the louvers, whereby the latter are easily and economically assembled into blinds of any desired size, and the desired correlation of the spacing and angular setting of the louvers within the frame may be readily etfected. A particular problem heretofore encountered in blinds of the slat or louver type has been their relatively high cost of production, due largely to the rather complicated methods employed in mounting the slats or louvers. The blinds or shutters herein disclosed obviate these disadvantages, while at the same time providing a structurally strong unit capable of withstanding considerable abuse. Furthermore, the construction is such that rattling of the louvers in a wind is effectively prevented. The louvers may be made of any suitably stiff material such as wood, metal or plastic. They may either be plane, or they may be made convex, or of other non-planar configuration, if desired, to give added strength. In any event, it is desirable that they be as thin as possible to reduce to a minimum the impedance of light entering from desired directions and, correspondingly, the interference with vision in directions parallel to the planes of the louvers. Also, the louvers may be completely opaque or, in some instances, it may be desirable to make them of translucent material such as a plastic to provide a diffused light transmitted through the louvers in addition to that reflected from the louver surfaces.

Other objects and advantages of the invention will be apparent from the following description of particularly suitable commercial installations embodying the principles of the invention, and shown in the accompanying drawings.

In the drawings Fig. l is a perspective view, looking toward the front, of one wall of a room in which blinds of the present invention are disposed across each of the windows;

Fig. 2 is a perspective view of the blinds looking toward the rear of the same room;

'Figs. 3 and 4 are diagrammatic plan views showing the angles of direct light interception provided by adjacent pairs of blind louvers or slats set at different angles to the plane of the window and at different distances apart;

Fig. 5 is a cross-sectional plan view of a blind of the type shown in Figs. 1 and 2, taken on line 5-5 of Fig. 1;

Fig. 6 is a plan view similar to that of Fig. 5 except that the frame of the blind has been shifted to dispose the slats or louvers at a more acute angle;

Fig. 7 is an enlarged fragmentary view of a blind shown in Fig. 1 showing details of louver mounting;

Fig. 8 is an enlarged end elevational view, partly broken away, of a blind showing further details of the louver mounting arrangement; and

Fig. 9 is a view similar to that of Fig. 7 but showing a modified construction.

A typical installation of the novel light-controlling blinds is shown in Figs. 1, 2 and 5 through 9. Each of blinds 40 comprises a plurality of thin metal slats or louvers 41 held in spaced, parallel, vertical alignment across the face of a window. These louvers 41 are held in this position by edgewise engagement with a frame structure consisting of a pair of parallel longitudinal members 42 connected at their ends to transverse member 43 to form a parallelogram. Normally two supporting frame structures are sufficient to mount the blind in front of a window although in some instances, depending upon the length of louvers'41, additional frames may be required to give sufficient rigidity to the assembled blind. Longitudinal members 42 are angle irons which are secured to transverse members 43 so that one of the legs of each angle is directed horizontally inward toward the other and each is provided along its length with a series of evenly spaced, arcuate shaped notches 44. Louvers 41 are also notched on opposite edges, as at 45, adjacent their upper and lower ends. In the assembled blind, the louvers are suspendedbetween longitudinal members 42 by interlocking engagement of notches 45 and a cooperating pair of opposed notches 44 in longitudinal members 42. In this manner each louver is gripped at opposed points on its opposite edges by the longitudinal members 42, the latter being held in spaced, parallel arrangement by transverse members 43 so that they cannot seperate and thus allow notches 45 in the louvers to become disengaged from notches 44 in members 42. In order to prevent binding of the louvers between members 42, the latter are so held that the distance between the back or inner edges 44a of cooperating opposed notches 44 is greater than the width between the inner edges 45a of opposite notches 45 in louvers 41, but less, of course, than the full width of louvers 41 so that the latter cannot drop out from between members 42. This arrangement permits a small amount of side play between the louvers and members 42. This slight tolerance is especially necessary where metal louvers are employed in order to accommodate the thermal expansion and contraction which occurs in such louvers, and in any event is generally desirable in all cases where, as hereinafter explained, the blind is constructed to provide for the simultaneous angular adjustment of the assembled louvers, as may be desirable in some instances.

Connection of the longitudinal members 42 to transverse members 43 may be accomplished in any suitable manner, and where the blind is not designed to permit adjustment of the angular setting of the louvers after assembly, the frame members may be riveted or welded together after positioning the louvers between the longitudinal members. Preferably, however, the members are held in fixed angular relationship by a plate 47 riveted to two of the frame members. As shown in Fig. 9, plate 47 may itself take the place of one of the transverse members 43.

As shown in Figs. 5 through 7, blind 40 may also be constructed to permit the simultaneous adjustment to substantially any desired angular setting of all the louvers in the completely assembled structure. To accomplish this, transverse members 43 are secured to longitudinal members 42 by pivot pins 48, thus permitting the longitudinal and transverse members to assume the form of an infinite number of parallelograms by longitudinal movement of one member 42 relative to the other. By this arrangement, the louvers pivot at the edges 44a and 45a of interengaged notches 44 and 45, respectively, and are turned to various angles within the frame. Since the frame is always a parallelogram, the distance between the back edge 44a of a notch 44 in one member 42 and the same point in the cooperating notch 44 of the other member 42 will always remain the same, and the louvers 41 will therefore be kept engaged between the longitudinal members. A better interlocking engagement between louvers and the members 42 is obtained by providing inwardly projecting shoulders 44b at the mouth of notches 44. These shoulders serve to prevent the louvers from slipping or snapping out of the notch when the louvers are set over at an acute angle within the frame as shown in dotted lines in Fig. 7. Furthermore, in order to prevent binding between the margin of the louver and the edge of notches 44, one shoulder of these notches may be offset, as at 44c, from its adjacent shoulder 44b and the edge of the angle iron cut away at 44d to provide additional clearance for the back of the louver when it is moved over to its aforesaid acute angular position.

An arrangement for facilitating the installation of louvers 41 between frame members 42 is also shown in detail in Fig. 7, in which one of members 42 is slotted at 42a to permit lateral reception of its respective pivot pin 48, and a spring 49 is connected between members 42 to retain pin 48 in slot 42a. By simply spreading members 42 apart against the tension of spring 49, louvers 41 may be disengaged from notches 44 and quickly removed and replaced within the frame.

In order to facilitate an understanding of the manner of designing a blind to effect the desired sunlight control for a particular installation, the following specific example is given as typical. A schoolroom in a building located on a parallel of latitude north of the equator has windows which face directly south. Normally, of course, direct sunlight will enter such a room during most of the day and it is desired to exclude the direct rays in order to reduce the possibility of causing eyestrain, as well as to eliminate unwanted, localized heating effects, while classes are in session. For the present example it is as sumed that the classroom is unoccupied during a mid day period extending from 11:00 a. m. to 1:00 p. m. and that direct sunlight may be permitted to enter during this period. It is assumed also that the louvers available from which the blind is to be constructed are manufactured in a single width only. This being so, it is apparent that the control afforded by the blind must be elfected entirely by the spacing and angular setting of the individual louvers within their supporting frame.

in the following description, and elsewhere in the present specification, a louver, in many instances, is spoken of as lying in a plane. It is apparent however that louvers having a convexity, or other non-linear form in transverse cross-section, cannot actually lie in a single plane, and the term plane of the louvers is therefore used to mean the plane in which opposite longitudinal edges of the louvers lie, and as shown in Figs. 3 and 4 is designated plane L.

The proper spacing and setting of the louvers in the frames is determined by first measuring the azimuthal positions of the sun at the two limits of the predetermined period for which direct rays are to be admitted. This may be done by actual measurement or it may be calculated from data obtainable from standard sources. In this instance these limits have been assumed as 11:00 a. m. and 1:00 p. m. and the angular position of the sun with respect to the plane W of the window at these two times is shown in Fig. 3. The variables of louver spacing and angular setting in the vertical axis are of course mutually dependent and change, for the same time lapse, with each different period of the day. One practical way of correlating these variables simply for a given installation is to plot the problem graphically, as in Figs. 3 and 4. As there shown, the spacing and angular setting is determined so that the diagonals lying in a plane perpendicular to the length of the louvers, when drawn between any pair of adjacent louvers, will intercept the azimuthal positions of the sun at the respective limits of the period for which direct sunlight is to be allowed to pass through the blind. For most practical purposes, the diagonals drawn through the diagonally opposite edges of adjacent louvers may be used for plotting the desired spacing and angular setting. It will be apparent, however, that this is an approximation only and is not strictly accurate except where the louvers are plane. Where the louvers are of convex or of other cross-sectional shape, this assumption will no longer be correct, and the error introduced will depend on the amount of deviation in the surface of the louver from a plane. In such cases the diagonals drawn from the edges of one louver, at its concave side, tangent to the convex face of the louver adjacent that side, will determine accurately the angular limits in azimuth of maximum intensity of direct light transmission for that particular form of louver.

Figs. 3 and 4 are of course purely diagrammatic since, for all practical purposes, the distance of the sun from the plane of the window may be considered as infinite. For this reason, it will be seen that for any given position of the sun, the difference in the angle a measured in azimuth between plane W and lines drawn from the sun to any point on or closely adjacent the surface of the window will be so negligible that it may be completely disregarded. The same is true with regard to angle c. All the louvers in a blind may therefore be set in their vertical axes at the same angle with respect to plane W without introducing any appreciable error. Since the example here given assumed that the window faced due south, it will be seen that the planes L of the louvers in this instance will be at right angles to plane W and, since the sun moves 15 in each hour, the angle b formed at the intersection of the aforesaid diagonals will be 30. Should it be desired to permit direct rays to enter only between 11:30 a. m. and 12:30 p. In. for the same window, the spacing of the louvers should be adjusted so that the angle of intersection of the diagonals is 15; that is, the spacing of the louvers in this case would be just half of that in the preceding example.

As a further example, assume that entrance of direct sunlight is to be permitted during a morning recess period lasting from 10:00 a. m. to 10:30 a. m. Again the angular position of the sun with respect to plane W of the window is determined for each of these two times and the spacing of the louvers is adjusted to make the diagonals drawn through opposite edges of adjacent louvers coincide with these angles. if the window is again assumed to be facing due south, it will be seen, as shown in Fig. 4, that in this instance the planes L will no longer intersect plane W at right angles but at some other angle depending upon the exact meridian of longitude on which the building is located. The blind can of course be adapted for windows having any exposure from which direct rays of the sun can enter, the spacing and angular setting of the louvers in each instance being such that the diagonals drawn through the opposite edges of adjacent louvers coincide, respectively, with the lines drawn from the particular window to the suns position at the limits of the desired period.

In the foregoing examples, it has been assumed that the width of the louvers which were available was fixed, it being desirable from economical considerations to limit the number of different widths in which the louvers are manufactured. Obviously, however, louvers of various widths may be employed and the spacing adjusted accordingly. Additional factors which must be considered in this connection are the fact that more louvers of a narrow width will be required to elfect the desired control than will be needed where louvers of greater width are employed; that is, the spacing between adjacent louvers will decrease proportionately to the decrease in width of the louvers employed for any given sunlight control problem. And generally speaking, the greater the number of louvers used, the greater will be the etfect of impairing the vision through the blind, even in directions parallel to the planes of the louvers. Furthermore the width has, of course, a direct effect upon the stillness or rigidity of the louver.

It has been found in practice that a louver having a width of about 2 inches, and having a convexity of about one-sixteenth to three thirty-seconds of an inch at the midpoint, is generally suitable for most purposes. Louvers made of aluminum alloy are particularly suitable for use in a blind of the present construction, since it is practical to employ relatively thin sheet stock of such alloy in producing the louvers. For example, sheet stock having a thickness of 0.010 inch is quite suitable, especially where the completed louver is made with the slight convexity suggested above and illustrated in the drawings.

This provides a louver of extremely light weight and sufficient flexibility for such slight accommodation as may be necessary when it is installed in its supporting frame, without at the same time having .it subject to the disadvantages of insufficient rigidity and undesirable bending and flexing due to drafts coming in an open window. Other widths, thicknesses and convexity may, of course, be used, those mentioned above being merely typical of what has been found practical in good commercial practice.

Consideration must also be given to the problem of preventing undesirable glare by reflectance from the louver surfaces themselves. This may usually be controlled conveniently by painting, etching or otherwise finishing the surfaces of the louvers with a flat or matte finish to effect a diffusion of the light striking these surfaces. In some instances, visibility characteristics may be improved by providing the louvers with a tinted surface, as for example with a pale green surface color. And where the louvers are convex in cross section, they should be positioned in their supporting frame so that the concave surface is directed away from the occupants in the room, in order to avoid annoyance from internal reflection between adjacent louvers.

From the foregoing general considerations, it will be apparent that various specific modifications may be made in the construction of the blind here disclosed without departing from the inventive concept of the present invention. Thus, the interengaging notches 44 and 45 illustrated in Figs. 7 and 8 more particularly can be replaced by ball and socket connections, for example. So also, the shoulders 44b of both members 44 may be offset and the adjacent edge of the louver cut away to facilitate angular settings of the louvers on both sides of the perpendicular. Or the louvers may be supported by engagement at points located at their extreme ends, as by means of small longitudinal projections from each end of a louver, the projections being adapted to be engaged in sockets provided in the frame members. In some instances it is possible, depending upon the particular exposure of the window, to construct a blind of the present type in which the louvers may be moved to and are retained in either of two preset angular positions in order to provide particular lighting control at different times of the day. Such a modification is sometimes quite advantageous at points having long periods of direct sunlight exposure, as in the case of a direct southern exposure in buildings located in the northern hemisphere. Thus two separate periods of direct sunlight admission may be effected, one in the morning and another in the afternoon, for example. Quite obviously also, the blinds may be made in a single section instead of the two Sections shown in Fig. 1. It is apparent therefore that the invention is not limited to the specific example illustrated and described above, but is susceptible to such other modifications and changes as fall within the scope of the appended claims.

What is claimed is:

1. A blind for controlling the light permitted to enter a room through a window, which comprises a plurality of slat-like louvers supported in parallelly-spaced, vertical arrangement across the face of said window, a frame for supporting said louvers, said frame comprising longitudinal members and transverse members connected together in alternation at their ends to form a parallelogram disposed in a horizontal plane substantially perpendicular to that of said window, said louvers being disposed between and in edgewise engagement with opposite longitudinal members of said frame, pairs of cooperating indentations along the adjacent inner edges of said longitudinal members, and indentations at opposite edges of each of said louvers, the indentations in said louvers being adapted and arranged for interlocking engagement with a pair of respectively cooperating indentations in said longitudinal members to support said louvers in depending vertical position in said frame.

2. A blind, as defined in claim 1, which includes a pair of said supporting frames, one of said frames engaging said louvers near their upper ends while the other of said frames engages said louvers near their lower ends.

3. A blind, as defined in claim 1, in which said frame members are connected together at their ends, and means for positively locking said members in a given angular relation.

4. A blind, as defined in claim 1, wherein the connection between one of said longitudinal and transverse members is in the form of a pin and slot construction, and spring means for yieldingly holding the pin normally engaged by the slot.

5. A blind, as defined in claim 3, wherein said means for locking said members comprises one of said transverse members, said member being secured at least at three points to two of said longitudinal members, two of said points being on the same member.

6. A blind, as defined in claim 1, in which said indentations in said longitudinal members are notches having a generally arcuate-shaped, main body portion recessed into said longitudinal members from the edge thereof, said indentations having shoulders formed in said longitudinal members at either side of said notches which shoulders project partially across said notches to form a restricted entrance to the main body of said notches.

7. A blind, as defined in claim 6, in which said shoulders are off-set in said longitudinal members and a portion of said members at a side of said notches is cut away.

8. A blind for controlling the light permitted to enter a room through a window, which comprises a plurality of slat-like louvers supported in parallelly-spaced, vertical arrangement across the face of said window, a frame for supporting said louvers, said frame comprising longitudinal members and transverse members connected together in alternation at their ends to form a parallelogram disposed in a horizontal plane substantially perpendicular to that of said window, said louvers being disposed transversely of their length between and in edgewise engagement with opposite longitudinal members of said frame, means along adjacent inner edges of said longitudinal members for engaging said louvers, and means at opposite edges of each of said louvers for receiving said first means in interlocking engagement to support said louvers in depending vertical position in said frame.

9. A window shutter comprising a plurality of slat-like louvers and a frame for supporting said louvers in spaced, parallel relation, said frame comprising longitudinal members and transverse members connected together in alternation at their ends to form a parallelogram disposed in a horizontal plane substantially perpendicular to that of said window, said louvers being disposed transversely of their lengths between and in edgewisc engagement with the adjacent inner margins of opposite longitudinal members of said frame, engaging means along said adjacent edges of said longitudinal members for engaging said louvers, and cooperating engaging means at opposite edges of said louvers for receiving said first means, both means being held in interlocking engagement by said transverse members.

References Cited in the file of this patent UNITED STATES PATENTS 1,677,910 Wills July 24, 1928 1,713,337 Hibbard May 14, 1929 1,718,754 Molina June 25, 1929 2,173,275 Houmere Sept. 19, 1939 2,238,648 Kallio Apr. 15, 1941 2,288,521 Gregory June 30, 1942 2,546,335 Friend Mar. 27, 1951 2,552,406 Chartoff May 8, 1951 FOREIGN PATENTS 101,544 Australia June 28, 1936 44,820 Netherlands Jan. 16, 1939 

